Imaging apparatus and imaging system

ABSTRACT

An imaging apparatus comprises a lens optical system including a lens and having first through nth optical regions (n is an integer equal to or greater than 2), an image sensor including pixel groups each including first through nth pixels, an optical element array disposed between the lens optical system and the image sensor and including optical components each guiding light that has passed through the first through nth optical regions to the respective first through nth pixels in each of the pixel groups, and an optical absorption member on which light reflected by the imaging surface of the image sensor is incident. The optical absorptance of the optical absorption member is substantially uniform across the entire wavelength bands of light that passes through the first through nth optical regions and is substantially uniform across the entire optical absorption member.

BACKGROUND

1. Technical Field

The present disclosure relates to imaging apparatuses, such as cameras,and imaging systems that include the imaging apparatuses.

2. Description of the Related Art

In recent years, image sensing cameras have been being researched anddeveloped. For example, an image of an object is obtained by imagingunder a plurality of imaging conditions, such as the polarizationcondition of light used in imaging and the wavelength of the light. Theimage is then analyzed and information on the object is obtained.

Examples of conventional image sensing cameras include a multibandcamera, which can obtain a two-dimensional spectral image of an objectthrough a single instance of imaging. Such a multiband camera isdisclosed, for example, in U.S. Pat. No. 7,433,042 and Japanese PatentNo. 5418392. In addition, Japanese Patent No. 5001471 discloses animaging apparatus that includes a spectral filter array disposed at aposition of an entrance pupil of an imaging optical system and amicrolens array disposed in the vicinity of an image sensor. Light raysthat have been dispersed by the spectral filter array are guided todifferent pixels by the microlens array, and thus a desired spectralimage can be obtained.

Hereinafter, an exemplary configuration of a conventional multibandcamera will be described.

The multiband camera disclosed in Japanese Patent No. 5418932 dividesthe wavelength range of light to be used to image an object into four ormore mutually different wavelength bands and images the object in thesewavelength bands. The multiband camera includes a band-pass filter arraydisposed at a position of a pupil of an optical system, a microlensarray, a photoelectric conversion element constituted by a plurality ofpixels that are arrayed two-dimensionally, and a measurement unit thatmeasures the spectral intensity of a light beam from the object.

The band-pass filter array includes four or more band-pass filters thattransmit light in respective four or more divided wavelength bands. Thephotoelectric conversion element is disposed around the focal point ofthe microlens array and at a position where the photoelectric conversionelement is conjugate with the band-pass filter array or in the vicinityof such a position. Light beams that have passed through the band-passfilter array are then guided by the microlens array to the plurality ofpixels that are arrayed two-dimensionally. The measurement unit measuresthe spectral intensity of the light beams from the object on the basisof signals outputted from the plurality of pixels corresponding to therespective band-pass filters in the band-pass filter array.

SUMMARY

In one general aspect, the techniques disclosed here feature an imagingapparatus that includes a lens optical system, an image sensor, anoptical element array, and an optical absorption member. The lensoptical system includes a lens and has optical regions, and the opticalregions include first through nth optical regions, in which n is aninteger equal to or greater than 2. The image sensor, on which lightthat has passed through the first through nth optical regions isincident, includes pixel groups and has an imaging surface that reflectsa part of the light that has passed through the first through nthoptical regions. The pixel groups each include n pixels of first throughnth pixels. The optical element array, in which optical components arearrayed, is disposed between the lens optical system and the imagesensor. The optical components each guide the light that has passedthrough the first through nth optical regions to the respective firstthrough nth pixels in each of the pixel groups. The part of the lightthat has passed through the first through nth optical regions and hasbeen reflected by the imaging surface is incident on the opticalabsorption member. An optical absorptance of the optical absorptionmember is substantially uniform across the entire wavelength bands ofthe light that passes through the first through nth optical regions andis substantially uniform across the entire optical absorption member.

According to an aspect of the present disclosure, an occurrence of ghostlight can be suppressed.

It should be noted that general or specific embodiments may beimplemented as a system, a method, an integrated circuit, a computerprogram, a storage medium, or any selective combination thereof.

Additional benefits and advantages of the disclosed embodiments willbecome apparent from the specification and drawings. The benefits and/oradvantages may be individually obtained by the various embodiments andfeatures of the specification and drawings, which need not all beprovided in order to obtain one or more of such benefits and/oradvantages.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram illustrating an imaging apparatusaccording to a first exemplary embodiment;

FIG. 2 is a perspective view of a band-pass filter array;

FIG. 3 is a perspective view illustrating an exemplary configuration ofan optical element array and an image sensor;

FIG. 4 is a perspective view for describing a relation between a givenmicrolens in an optical element array and a plurality of pixelscorresponding to the given microlens;

FIG. 5 is a perspective view illustrating an exemplary configuration ofan image sensor in which a microlens is disposed over the surface of thepixels;

FIG. 6 is a perspective view illustrating an exemplary configuration inwhich an optical absorption filter is integrated with an image sensor;

FIG. 7 is a schematic diagram for describing a mechanism by which aghost image appears in an imaging apparatus that does not include anoptical absorption filter;

FIG. 8 is a schematic diagram for describing a mechanism by which ghostlight is removed in an imaging apparatus according to the firstexemplary embodiment;

FIG. 9 is a schematic diagram illustrating an imaging apparatusaccording to a second exemplary embodiment;

FIG. 10A is a schematic diagram illustrating vibrations of the electricfield of signal light that has passed through a polarizer in the imagingoptical system illustrated in FIG. 9;

FIG. 10B is a schematic diagram illustrating vibrations of the electricfield of the signal light that has passed through a quarter-wave platein the imaging optical system illustrated in FIG. 9;

FIG. 10C is a schematic diagram illustrating vibrations of the electricfield of ghost light in the imaging optical system illustrated in FIG.9;

FIG. 10D is an enlarged schematic diagram illustrating part of animaging optical system illustrated in FIG. 9;

FIG. 11A is a schematic sectional view illustrating an imaging apparatusaccording to a third exemplary embodiment;

FIG. 11B is a front view illustrating a positional relation betweenoptical regions in an optical region and openings in a stop;

FIG. 12A is an enlarged view of an optical element array and an imagesensor illustrated in FIG. 11A;

FIG. 12B illustrates a plurality of pixels in an image sensor;

FIG. 13A is an illustration for describing ghost light occurring in acase in which the shape of each optical region is a circle;

FIG. 13B is an illustration for describing ghost light occurring in acase in which each optical region has the shape illustrated in FIG. 11B;

FIG. 14A is a schematic sectional view illustrating an imaging apparatusaccording to a fourth exemplary embodiment;

FIG. 14B is a front view illustrating a positional relation betweenoptical regions in an optical region and openings in a stop;

FIG. 15A schematically illustrates crosstalk light between adjacentpixels occurring in a case in which a light-blocking region is notprovided;

FIG. 15B schematically illustrates crosstalk light between adjacentpixels occurring in a case in which a light-blocking region is provided;

FIG. 16A is an illustration for describing ghost light occurring in acase in which a light-blocking region is not provided;

FIG. 16B is an illustration for describing ghost light occurring in acase in which a light-blocking region is provided; and

FIG. 17 is a schematic diagram illustrating an overall configuration ofa spectral imaging system according to a fifth exemplary embodiment.

DETAILED DESCRIPTION

For example, an absorptive color filter or an interference filter can beused as the band-pass filter described above. An absorptive color filtermay be formed of a material having optical absorption characteristicswith wavelength dependence. Meanwhile, an interference filter may beformed by an optical multilayer film.

The design flexibility of an interference filter is high in terms of thelight utilization efficiency and spectral transmission characteristics.In addition, an interference filter advantageously functions as anarrow-band filter that transmits only light at a specific wavelength.Accordingly, an interference filter is used more frequently than anabsorptive color filter as a band-pass filter for a multiband camera.

Hereinafter, a problem that the inventor of the present disclosure hasconsidered will be described.

An interference filter transmits light in a predetermined wavelengthband. Meanwhile, light in a wavelength band other than the wavelengthband that the interference filter transmits is reflected with highreflectance by the interference filter. Due to such characteristics,disposing an interference filter in an optical path may be a significantcause for ghost light to be generated. Specifically, for example, lightin a given wavelength band A passes through a band-pass filter aprovided in a given region of a band-pass filter array. That light,however, is reflected with high reflectance by a band-pass filter bprovided in another region.

In this manner, for the light in the wavelength band A, the band-passfilter b functions as a reflection mirror disposed in an optical path.As a result, ghost light is likely to be generated. For example, some ofthe light in the wavelength band A that has passed through a firstband-pass filter and has reached a photoelectric conversion elementthrough a microlens array is specularly reflected by the surface of thephotoelectric conversion element. The reflected light, as returninglight, reaches a second band-pass filter that is disposed in theband-pass filter array at a position that is rotationally symmetric tothe first band-pass filter with respect to the center axis of theentrance pupil. The second band-pass filter transmits light in awavelength band B. The returning light is thus reflected again by thesecond band-pass filter and is then incident on the photoelectricconversion element. In this manner, the returning light becomes ghostlight and a ghost image appears. In the specification of the presentdisclosure, ghost light primarily refers to the above-describedreturning light. In addition, a ghost image refers to an image thatappears due to the ghost light.

The returning light that is incident on the photoelectric conversionelement is superposed on light that serves as a basis of two-dimensionalspectral information of an object. As a result, the superposed lightappears as a ghost image in the measurement result. The appearance of aghost image is a fundamental problem of the multiband camera disclosedin U.S. Pat. No. 7,433,042 or Japanese Patent No. 5418392. This problem,however, is not even mentioned in U.S. Pat. No. 7,433,042 or JapanesePatent No. 5418392. In addition, even in a case in which an opticalfunction element, aside from the band-pass filter, having highreflectance is disposed at the position of the pupil, as in the casedescribed above, a ghost image appears. Examples of optical functionelements having high reflectance include a wire-grid polarizer, which isa reflective polarizing element. It is to be noted that the mechanism bywhich a ghost image is generated will be described later in detail.

With the conventional techniques described above, it is desired that anoccurrence of ghost light be suppressed.

In view of such a problem with the conventional techniques, the inventorof the present disclosure has conceived of an imaging apparatus that hasa novel structure.

A non-limiting, exemplary embodiment of the present disclosure providesan imaging apparatus and an imaging system that can suppress anoccurrence of ghost light.

The present disclosure includes an imaging apparatus and an imagingsystem set forth in the following items.

Item 1

A imaging apparatus that includes a lens optical system that includes alens and has optical regions, the optical regions including firstthrough nth optical regions, n being an integer equal to or greater than2; an image sensor on which light that has passed through the firstthrough nth optical regions is incident, the image sensor includingpixel groups and having an imaging surface that reflects a part of thelight that has passed through the first through nth optical regions, thepixel groups each including n pixels of first through nth pixels; anoptical element array in which optical components are arrayed, theoptical element array being disposed between the lens optical system andthe image sensor, the optical components each guiding the light that haspassed through the first through nth optical regions to the respectivefirst through nth pixels in each of the pixel groups; and an opticalabsorption member on which the part of the light that has passed throughthe first through nth optical regions and has been reflected by theimaging surface is incident, wherein an optical absorptance of theoptical absorption member is substantially uniform across the entirewavelength bands of the light that passes through the first through nthoptical regions and is substantially uniform across the entire opticalabsorption member. In the lens optical system of the imaging apparatusset forth in Item 1, the plurality of optical regions may be disposed soas to be substantially perpendicular to an optical axis of the lens. Inother words, the angle formed by the optical axis of the lens and theplurality of optical regions may be from 85° to 95° inclusive.

According to the imaging apparatus set forth in Item 1, ghost light canbe suppressed effectively, and a high-precision image with little ghostimage can be obtained.

Item 2

The imaging apparatus set forth in Item 1, wherein the opticalabsorption member is disposed between the optical regions and the imagesensor and absorbs at least first light in a first wavelength band andsecond light in a second wavelength band, the first light being capableof passing through the first optical region, the second light beingcapable of passing through the second optical region.

According to the imaging apparatus set forth in Item 2, an imagingapparatus that can obtain a high-precision image with little image noiseand little ghost image can be provided. For example, an imagingapparatus for high-precision image sensing can be provided.

Item 3

The imaging apparatus set forth in Item 2, wherein at least one selectedfrom the group of the first and second optical regions has opticalcharacteristics of transmitting visible light, and wherein the opticalabsorption member absorbs at least the visible light.

According to the imaging apparatus set forth in Item 3, an imagingapparatus that can obtain a high-precision image with little image noiseand little ghost image in imaging in which visible light is used can beprovided.

Item 4

The imaging apparatus set forth in Item 2 or 3, wherein the lens opticalsystem further includes a stop, and wherein the optical regions aredisposed at the stop or in the vicinity of the stop.

Item 5

The imaging apparatus set forth in any one of Items 2 through 4, whereinthe first optical region differs from the second optical region in termsof at least one selected from the group of spectral transmittancecharacteristics and polarization characteristics.

According to the imaging apparatus set forth in Item 5, an imagingapparatus that can simultaneously capture images that differ in terms ofat least one selected from the group of the spectral transmittancecharacteristics and the polarization characteristics through a singleinstance of imaging and that can also obtain a high-precision image withlittle image noise and little ghost image can be provided.

Item 6

The imaging apparatus set forth in any one of Items 1 through 5, whereinthe optical absorptance of the optical absorption member is uniformacross the entire wavelength bands of the light that passes through thefirst through nth optical regions, or a relative error in the opticalabsorptance in the entire wavelength bands is within 10%, and whereinthe optical absorptance of the optical absorption member per unit areais uniform across the entire optical absorption member, or a relativeerror in the optical absorptance of the entire optical absorption memberper unit area is within 10%.

According to the imaging apparatus set forth in Item 6, an imagingapparatus that can effectively suppress ghost light and that can obtaina high-precision image with little ghost image can be provided.

Item 7

The imaging apparatus set forth in any one of Items 2 through 4 furtherincludes at least two narrow band-pass optical filters disposed in theoptical regions, the at least two narrow band-pass optical filtersdiffer in transmission wavelength bands.

According to the imaging apparatus set forth in Item 7, an imagingapparatus that can simultaneously capture narrow-band images that differin terms of the spectral transmittance characteristics through a singleinstance of imaging and that can also obtain a high-precision image withlittle image noise and little ghost image can be provided.

Item 8

The imaging apparatus set forth in any one of Items 2 through 7, whereinthe optical element array is a lenticular lens.

According to the imaging apparatus set forth in Item 8, light that haspassed through the first and second optical regions can efficiently beguided one-dimensionally to the respective first and second pluralitiesof pixels.

Item 9

The imaging apparatus set forth in any one of Items 2 through 7, whereinthe optical element array is a microlens array.

According to the imaging apparatus set forth in Item 9, light that haspassed through the first and second optical regions can efficiently beguided two-dimensionally to the respective first and second pluralitiesof pixels.

Item 10

The imaging apparatus set forth in any one of Items 2 through 9, whereinthe optical element array is integrated with the image sensor.

According to the imaging apparatus set forth in Item 10, it becomesunnecessary to adjust the positioning of the optical element array andthe image sensor, and a change over time in the positional relationbetween the optical element array and the image sensor can be reduced.

Item 11

The imaging apparatus set forth in any one of Items 2 through 9 furtherincludes a microlens provided between the optical element array and theimage sensor, and wherein the optical element array is integrated withthe microlens and the image sensor.

According to the imaging apparatus set forth in Item 11, the efficiencyof light incident on the image sensor improves due to the microlens, andthe S/N ratio of a video signal can be improved.

Item 12

The imaging apparatus set forth in any one of Items 2 through 9, whereinthe optical absorption member is integrated with the image sensor.

According to the imaging apparatus set forth in Item 12, it becomesunnecessary to adjust the positioning of the optical absorption memberand the image sensor, and a change over time in the positional relationbetween the optical absorption member and the image sensor can bereduced.

Item 13

The imaging apparatus set forth in any one of Items 2 through 12,wherein the optical absorption member is an absorptive neutral density(ND) filter, and a ratio of a quantity of emitted light that is emittedfrom the ND filter to a quantity of incident light that is incident onthe ND filter is from 30% to 50% inclusive.

According to the imaging apparatus set forth in Item 13, an imagingapparatus that includes a commercially available ND filter and canobtain a high-precision image with little image noise and little ghostimage can be provided.

Item 14

The imaging apparatus set forth in any one of Items 2 through 11,wherein the optical absorption member includes an absorptive linearpolarizer that transmits vibrating light that vibrates in a direction ofa polarization axis, and a phase plate that converts linearly polarizedlight to circularly polarized light or to elliptically polarized light,and wherein the absorptive linear polarizer is disposed in the opticalabsorption member toward a side of the optical regions, and the phaseplate is disposed in the optical absorption member toward a side of theimage sensor.

According to the imaging apparatus set forth in Item 14, an imagingapparatus that can obtain a high-precision image with little image noiseand little ghost image can be provided.

Item 15

The imaging apparatus set forth in Item 14, wherein the phase plate is aquarter-wave plate.

According to the imaging apparatus set forth in Item 15, an imagingapparatus that includes a commercially available quarter-wave plate andcan obtain a high-precision image with little image noise and littleghost image can be provided.

Item 16

The imaging apparatus set forth in Item 14, wherein the phase plate isan achromatic wave plate.

According to the imaging apparatus set forth in Item 16, an imagingapparatus that can obtain a high-precision image with little image noiseand little ghost image even when an imaging wavelength band is broad canbe provided.

Item 17

The imaging apparatus set forth in Item 2, wherein the first opticalregion has first spectral transmittance characteristics of transmittinga first near-infrared ray in the first wavelength band, and the secondoptical region has second spectral transmittance characteristics oftransmitting a second near-infrared ray in the second wavelength band,the second wavelength band being different from the first wavelengthband, and wherein the optical absorption member absorbs at least thefirst and second near-infrared rays.

According to the imaging apparatus set forth in Item 17, an imagingapparatus that can obtain a high-precision image with little image noiseand little ghost image in imaging in which near-infrared rays are usedcan be provided.

Item 18

The imaging apparatus set forth in Item 2, wherein n is 9, wherein, ineach of the pixel groups, the first pixel, the second pixel, the thirdpixel, the fourth pixel, the fifth pixel, the sixth pixel, the seventhpixel, the eighth pixel, and the ninth pixel are arrayed in a 3×3matrix, wherein the pixel groups are repeated in a row direction and ina column direction in the image sensor, wherein the optical elementarray is a microlens array that includes microlenses, wherein each ofthe microlenses in the microlens array corresponds to one of the pixelgroups, and wherein the optical absorption member absorbs at least thefirst light, the second light, third light in a third wavelength band,fourth light in a fourth wavelength band, fifth light in a fifthwavelength band, sixth light in a sixth wavelength band, seventh lightin a seventh wavelength band, eighth light in an eighth wavelength band,and ninth light in a ninth wavelength band, the third light beingcapable of passing through the third optical region, the fourth lightbeing capable of passing through the fourth optical region, the fifthlight being capable of passing through the fifth optical region, thesixth light being capable of passing through the sixth optical region,the seventh light being capable of passing through the seventh opticalregion, the eighth light being capable of passing through the eighthoptical region, and the ninth light being capable of passing through theninth optical region.

According to the imaging apparatus set forth in Item 18, an imagingapparatus that can capture an image having multiple spectralcharacteristics through a single instance of imaging and that can alsoobtain a high-precision image with little image noise and little ghostimage can be provided.

Item 19

An imaging apparatus includes a lens optical system; an image sensorthat receives light condensed by the lens optical system; and an opticalelement disposed between the lens optical system and the image sensor,the optical element absorbing at least visible light, the opticalelement having substantially uniform optical absorption characteristicsacross the entire region of the optical element through which the lightpasses.

According to the imaging apparatus set forth in Item 19, an imagingapparatus that can obtain a high-precision image with little image noiseand little ghost image can be provided.

Item 20

An imaging system includes an imaging apparatus set forth in any one ofItems 1 through 19; a signal processor adapted to process a pixel signaloutputted from the imaging apparatus to generate image information; anda display adapted to display an image corresponding to the imageinformation.

According to the imaging system set forth in Item 20, an imaging systemfor image sensing that includes an imaging apparatus capable ofobtaining a high-precision image with little image noise and littleghost image can be provided.

With an imaging apparatus according to an aspect of the presentdisclosure, for example, a plurality of images can be obtainedsimultaneously by a single imaging optical system under a plurality ofimaging conditions, such as the polarization condition of light used inimaging and the wavelength of the light. In addition, a ghost image canbe suppressed by the optical absorption member. As a result, an imagingapparatus that is capable of high-precision spectral imaging can beprovided.

Hereinafter, specific embodiments of the present disclosure will bedescribed with reference to the drawings. In the description to follow,identical or similar components are given identical referencecharacters. In addition, duplicate descriptions may be omitted. It is tobe noted that an imaging apparatus and an imaging system according toembodiments of the present disclosure are not limited to thoseillustrated hereinafter.

First Embodiment

FIG. 1 is a schematic diagram illustrating an imaging apparatus 100Aaccording to a first embodiment.

Hereinafter, the configuration of the imaging apparatus 100A will bedescribed with the direction of an optical axis 10, which is the centeraxis of the imaging apparatus 100A, set as a z-axis and with a planeorthogonal to the z-axis set as an xy-plane, as illustrated in FIG. 1.It is to be noted that an object 1 is illustrated in FIG. 1 so as tofacilitate understanding of a person skilled in the art. It is needlessto say that the object 1 is not a component of the imaging apparatus100A.

The imaging apparatus 100A includes a lens optical system L, an opticalabsorption member 6, an optical element array 7, and an image sensor 9.

The lens optical system L includes a first lens 2, a second lens 5, astop 3, and a band-pass filter array 4. The first lens 2 condenses lightfrom the object 1 and guides the light to the stop 3. The second lens 5condenses light that has passed through the band-pass filter array 4. Inthe specification of the present disclosure, the stop 3 or a region inthe vicinity of the stop 3 is referred to as an optical region.

The band-pass filter array 4 is disposed in the optical region along thexy-plane. The band-pass filter array 4 may be formed by a plurality ofband-pass filters. The optical region includes at least a first opticalregion and a second optical region that have different opticalcharacteristics.

The first lens 2 and the second lens 5 may each be constituted by asingle lens or by a plurality of lenses. In addition, the configurationmay be such that a plurality of lenses are disposed at front and backsides of the stop 3. If the range of the angle of view of imaging isnarrow, the first lens 2 may be omitted.

The optical element array 7 is, for example, a microlens array. Theoptical element array 7 is disposed at or in the vicinity of a focalpoint of the lens optical system L and is disposed between the lensoptical system L and the image sensor 9.

The image sensor 9 includes a plurality of pixels 8 disposed therein.The image sensor 9 includes at least a plurality of first pixels and aplurality of second pixels.

The optical element array 7 guides the light that has passed through thefirst optical region to the plurality of first pixels and guides thelight that has passed through the second optical region to the pluralityof second pixels.

The optical absorption member 6 is a member that may be formed of amaterial that absorbs light, and primarily absorbs reflected light froman imaging surface of the image sensor 9. Specifically, the opticalabsorption member 6 absorbs at least light in a first wavelength band(e.g., wavelength band of red), which is the wavelength band of thelight that has passed through the first optical region, and light in asecond wavelength band (e.g., wavelength band in blue), which is thewavelength band of the light that has passed through the second opticalregion. The optical absorption member 6 has substantially uniformoptical absorption characteristics (i.e., optical absorptance) across aregion therein through which light passes. In addition, the opticalabsorption member 6 has substantially the same optical absorptance inthe wavelength bands of the light that passes through the first andsecond optical regions.

That the optical absorptance is substantially uniform across a regionthrough which the light passes means that the optical absorptance perunit area is constant within the region through which the light passesor that a relative error in the optical absorptance per unit area iswithin 10% in the region through which the light passes. In addition,that the optical absorptance is substantially the same in the wavelengthbands of light that passes through the first and second optical regionsmeans that the optical absorptance is uniform across the entirewavelength bands of the light that passes through the first and secondoptical regions or that a relative error in the optical absorptance inthe stated wavelength bands is within 10%.

The optical absorption member 6 is disposed between the lens opticalsystem L and the optical element array 7. However, the configuration isnot limited thereto, and the optical absorption member 6 may, forexample, be disposed between the band-pass filter array 4 and the secondlens 5. It is sufficient if the optical absorption member 6 is disposedbetween the band-pass filter array 4 and the image sensor 9.

Subsequently, with reference to FIG. 2, the configuration of theband-pass filter array 4 will be described in detail.

FIG. 2 is a perspective view of the band-pass filter array 4.

In the present embodiment, an example in which the optical region isdivided into nine optical regions will be described. The number ofoptical regions into which the optical region is divided is not limitedto nine and can be any integer that is equal to or greater than two.

The band-pass filter array 4 is disposed in the optical region in thevicinity of the stop 3. The band-pass filter array 4 is constituted bynine rectangular band-pass filters 4 a through 4 i. The rectangularband-pass filters 4 a through 4 i are disposed in a 3×3 matrix along thexy-plane. The rectangular band-pass filters 4 a through 4 i are disposedin the respective nine optical regions. The rectangular band-passfilters 4 a through 4 i have mutually different optical transmissionwavelength bands.

For example, when the wavelength band to be used in imaging the object 1is in a range of visible light wavelengths, namely, from 380 nm to 750nm, transmission wavelength bands of equal widths can be assigned to therespective rectangular band-pass filters 4 a through 4 i. Specifically,a transmission wavelength band of 390 nm to 430 nm can be assigned tothe rectangular band-pass filter 4 a, and a transmission wavelength bandof 430 nm to 470 nm can be assigned to the band-pass filter 4 b. In asimilar manner, a transmission wavelength band of 470 nm to 510 nm canbe assigned to the band-pass filter 4 c. A transmission wavelength bandof 510 nm to 550 nm can be assigned to the band-pass filter 4 d. Atransmission wavelength band of 550 nm to 590 nm can be assigned to theband-pass filter 4 e. A transmission wavelength band of 590 nm to 630 nmcan be assigned to the band-pass filter 4 f. A transmission wavelengthband of 630 nm to 670 nm can be assigned to the band-pass filter 4 g. Atransmission wavelength band of 670 nm to 710 nm can be assigned to theband-pass filter 4 h. A transmission wavelength band of 710 nm to 750 nmcan be assigned to the band-pass filter 4 i.

In the exemplary configuration illustrated in FIG. 2, the rectangularband-pass filters 4 a through 4 i are disposed so as to be adjacent toone another. However, due to diffraction or scattering at an edge of aboundary portion, crosstalk of light transmitted through the band-passfilters may occur. Therefore, light-blocking regions may be provided atboundary portions of the rectangular band-pass filters 4 a through 4 iso as to reduce the crosstalk.

Subsequently, with reference to FIG. 3, the configuration of the opticalelement array 7 and the image sensor 9 will be described in detail.

FIG. 3 is a perspective view illustrating the configuration of theoptical element array 7 and the image sensor 9. As illustrated in FIG.3, in the present embodiment, the optical element array 7 is a microlensarray. Microlenses 11 constituting the microlens array are disposedtwo-dimensionally in the x-direction and the y-direction in the vicinityof the surface of the image sensor 9.

Several tens of hundred to several million microlenses 11 are disposedalong the xy-plane. The shape of each microlens 11 is, for example, acircle, a quadrangle, or a hexagon. The focal length of the microlenses11 is approximately from several tens to several hundreds ofmicrometers.

The microlenses 11 are disposed in the vicinity of the focal point ofthe lens optical system L. The real image of the object 1 is formed onthe microlenses 11. The plurality of pixels 8 are disposed in thevicinity of the focal point position of the microlenses 11.

The image sensor 9 is constituted by several hundreds of thousand toseveral tens of million pixels 8, which are photoelectric conversionelements, disposed along the xy-plane. The image sensor 9, for example,is a charge-coupled device (CCD) image sensor or a complementarymetal-oxide semiconductor (CMOS) image sensor.

FIG. 4 is a perspective view for describing a relation between a givenmicrolens 11 in the optical element array 7 (microlens array) and aplurality of pixels 8 corresponding to the given microlens 11.

A single microlens 11 corresponds to nine pixels 8 a through 8 i.Information for one pixel in each of a plurality of images capturedsimultaneously is obtained by a configuration unit illustrated in FIG.4.

The microlens 11 is formed with parameters, such as the refractiveindex, the distance from an imaging surface, and the radius ofcurvature, being set as appropriate. Light that has passed through thenine optical regions of the band-pass filters 4 a through 4 iillustrated in FIG. 2 is divided by the microlenses 11, and the lightrays are discretely incident on the respective nine pixels 8 a through 8i. It is to be noted that the number of pixels corresponding to a singlemicrolens 11 varies in accordance with the number of divided opticalregions.

Each of the plurality of pixels 8 converts light incident thereon into apixel signal corresponding to the intensity of the light throughphotoelectric conversion. A luminance signal of an image to be obtainedis based on this pixel signal. A signal processor (not illustrated)receives pixel signals, outputted from the image sensor 9, correspondingto the respective pixels 8. The signal processor obtains luminanceinformation of a pixel group corresponding to the pixel 8 a, illustratedin FIG. 4, in each of the microlenses 11 of the optical element array 7.The signal processor generates information on a two-dimensional image inthe first wavelength band from the obtained luminance information of thepixel group. The signal processor carries out similar processes for thepixel groups corresponding to the respective pixels 8 b through 8 iillustrated in FIG. 4. The signal processor outputs the two-dimensionalimage information in nine different wavelength bands. In this manner, byusing the imaging apparatus 100A, a plurality of images that are basedon information of light in different wavelength bands can be obtainedsimultaneously.

The signal processor may be constituted by hardware, such as asemiconductor element. The signal processor may typically be implementedby an image signal processor (ISP). The signal processor may also beimplemented by an arithmetic unit (e.g., microprocessor unit (MPU)), amemory, and software.

It is to be noted that light-blocking regions or blind sectors may beprovided, for example, at boundary portions of the pixels 8 a through 8i so that signal light from the microlens 11 is not incident onsurrounding pixels other than a predetermined pixel.

FIG. 5 is a perspective view illustrating the image sensor 9 in whichmicrolenses 13 are disposed on the surfaces of the respective pixels 8.As illustrated in FIG. 5, the microlenses 13 may be disposed on thesurfaces of the respective pixels 8. Through this configuration, theefficiency of light incident on the pixels 8 can be increased. A digitalmicrolens (DML), for example, can be used as the microlens 13. The DMLis formed by densely disposing concentric ring structures that aresmaller than the wavelength of the light. The DML condenses lightthrough a change in the effective refractive index distribution.

In the present embodiment, the optical absorption member 6 is disposedbetween the lens optical system L and the optical element array 7. Anoptical absorption filter can be used as the optical absorption member6. The optical absorption filter, for example, is an absorptive neutraldensity (ND) filter.

FIG. 6 is a perspective view illustrating an exemplary configuration inwhich an optical absorption filter is integrated with the image sensor9. As illustrated in FIG. 6, an optical absorption layer 14 functions asthe optical absorption filter. The optical absorption layer 14 may beintegrated with the image sensor 9. Through this configuration, theoptical system can be simplified, and the assembly and the adjustment ofthe optical system become easier.

Hereinafter, an effect of suppressing ghost light by using an opticalabsorption filter will be described in detail.

FIG. 7 is an illustration for describing a mechanism by which a ghostimage appears in an imaging apparatus that does not include an opticalabsorption filter. In FIG. 7, for simplicity, a focus is placed on lightfrom a given point on the object 1, and only a principal ray isillustrated. Hereinafter, with reference to that principal ray, amechanism by which a ghost image appears will be described.

The light from the object 1 passes, for example, through the first lens2, a band-pass filter 4A in the band-pass filter array 4, the secondlens 5, and the optical element array 7 in this order and reaches apredetermined pixel 8 in the image sensor 9. The predetermined pixel isa pixel 8A corresponding to the band-pass filter 4A.

Part of the light ray that travels toward the pixel 8A is reflected, forexample, by the optical element array 7 and/or the surface of the pixel8A. The reflected light becomes ghost light 15. The ghost light 15, forexample, passes through the second lens 5 and is incident on theband-pass filter array 4. In this case, part of the ghost light 15, forexample, reaches a band-pass filter 4B, which is different from theband-pass filter 4A.

The band-pass filter 4A and the band-pass filter 4B differ in terms ofthe wavelength band of light that they transmit. For example, due to thecharacteristics of a band-pass filter, such as an interference filterdescribed above, the band-pass filter 4B hardly transmits the ghostlight 15 that reaches the band-pass filter 4B. Most of the ghost light15 is thus specularly reflected by the band-pass filter 4B.

Thereafter, the ghost light 15 that has been reflected by the band-passfilter 4B again passes through the second lens 5. The transmitted ghostlight 15, for example, is then incident on a pixel 8B, which is disposedat a position different from the position where the pixel 8A isdisposed, through the optical element array 7. The pixel 8B is a pixelcorresponding to the band-pass filter 4B. The pixel 8B receives theghost light 15. As a result, a ghost image appears in a captured image.

FIG. 8 is an illustration for describing a mechanism by which the ghostlight 15 is removed in the imaging apparatus 100A according to thepresent embodiment. With reference to FIG. 8, an effect of the opticalabsorption filter serving as the optical absorption member 6 will bedescribed. As described above, an absorptive ND filter can be used asthe optical absorption filter.

The light from the object 1 passes, for example, through the first lens2, the band-pass filter 4A in the band-pass filter array 4, and thesecond lens 5, and then further passes through the optical absorptionfilter. The transmitted light reaches the pixel 8A corresponding to theband-pass filter 4A through the optical element array 7.

As described above, part of the light ray that has reached the pixel 8Ais reflected by the surface of the pixel 8A. The reflected light maybecome the ghost light 15. The ghost light 15 passes through the opticalabsorption filter and thus has its quantity of light reduced. Part ofthe ghost light 15 that has passed through the optical absorption filterpasses through the second lens 5 and reaches the band-pass filter array4B, which is different from the band-pass filter array 4A. Part of theghost light 15 is reflected by the band-pass filter array 4B and againpasses through the second lens 5. The ghost light 15 that has passedthrough the second lens 5 again passes through the optical absorptionfilter. As a result, the ghost light 15 has its quantity of lightfurther reduced. In the end, the ghost light 15, for example, reachesthe pixel 8B, which is disposed at a position different from theposition where the pixel 8A is disposed.

In this manner, the ghost light 15 passes through the optical absorptionfilter twice. In the specification of the present disclosure, a signalintensity corresponding to the quantity of light that contributes to acaptured image is referred to as the quantity of signal light for acaptured image, and a signal intensity corresponding to the quantity oflight that contributes to a ghost image is referred to as the quantityof signal light for a ghost image. When the transmittance of the opticalabsorption filter is represented by T (<1), the ratio of the quantity ofsignal light for a ghost image to the quantity of signal light for acaptured image is T² times greater in the configuration illustrated inFIG. 8 than in the configuration illustrated in FIG. 7.

Specifically, in the configuration illustrated in FIG. 7, for example,the ratio of the quantity of signal light for a ghost image to thequantity of signal light for a captured image may be 3%. In themeantime, in a case in which the optical absorption filter is disposedas illustrated in FIG. 8 and the transmittance T of the opticalabsorption filter is 50%, the ratio of the quantity of signal light fora ghost image to the quantity of signal light for a captured image is0.03×0.5×0.5=0.0075. In this manner, the ratio between the quantities ofsignal light can be reduced to 0.75%.

In addition, in a case in which the transmittance T of the opticalabsorption filter is 30%, the ratio of the quantity of signal light fora ghost image to the quantity of signal light for a captured image is0.03×0.3×0.3=0.0027. In this manner, the ratio between the quantities ofsignal light can be further reduced to 0.27%. When the above is takeninto consideration, the ratio between the quantities of signal light maybe from 30% to 50% inclusive.

In the present embodiment, the optical absorption filter has opticalabsorption characteristics of absorbing at least visible light. In orderto efficiently reduce ghost light, it is desirable that the wavelengthband of the optical absorption characteristics match the transmissionwavelength band (390 nm to 750 nm) of the band-pass filter array 4. Forexample, in a case in which a plurality of images that are based onlight in different transmission wavelength bands are to be obtainedsimultaneously by using visible light, as in the present embodiment, bydisposing an optical absorption filter, an influence of ghost light ofvisible light that contributes to image formation can be reduced.

In the meantime, a near-infrared (IR)-cut filter that transmits visiblelight and cuts near-infrared rays is typically used in a compact digitalcamera. An IR-cut filter cuts unnecessary light (near-infrared rays)that does not contribute to image formation. In this respect, theintended use of the optical absorption filter of the present disclosurediffers from that of the IR-cut filter.

According to the present disclosure, for example, a plurality of imagescan be captured simultaneously by using near-infrared rays instead ofvisible light. Near-infrared rays are light (electromagnetic waves) at awavelength in a range from approximately 700 nm to 2.5 μm. In a case inwhich near-infrared rays are used, transmission wavelength bands ofequal widths can be assigned to the respective rectangular band-passfilters 4 a through 4 i in the wavelength bands of the near-infraredrays. In addition, an optical absorption filter having opticalabsorption characteristics of absorbing at least near-infrared rays maybe used as the optical absorption member 6. Through this configuration,an influence of ghost light of near-infrared rays that contribute toimage formation can be suppressed efficiently.

According to the present embodiment, image information with littleinfluence of ghost light can be obtained through a simple configuration.

Hereinafter, modifications of the present embodiment will be described.

In the present embodiment, the widths of the transmission wavelengthbands of the respective band-pass filters 4 a through 4 i in theband-pass filter array 4 are set equally to 40 nm. The presentdisclosure is not limited thereto, and the transmission wavelength bandsof the respective band-pass filters 4 a through 4 i may be set inaccordance with the product specifications. For example, the widths ofthe transmission wavelength bands of the respective band-pass filters 4a through 4 i do not need to be equal to one another. The width of atransmission wavelength band may be set to several nanometers, and anarrow-band interference filter may be used as a band-pass filter.Through this configuration, pinpointing information on light havingcomponents of respective wavelengths can be obtained.

In addition, in the present embodiment, an example in which the ninerectangular band-pass filters are disposed in a 3×3 matrix has beenillustrated. Aside from such a configuration, for example, a pluralityof rectangular band-pass filters may be disposed in a 2×2 matrix, a 4×4matrix, or a 5×5 matrix. In such a case, the plurality of pixels 8 maybe disposed in accordance with the shape of the band-pass filter array4. In addition, the shapes of the band-pass filters do not need to beidentical, and may, for example, be a circle, a rectangle, or a polygon.

Furthermore, the wavelength band can be divided only in aone-dimensional direction. For example, a plurality of band-pass filtersmay be disposed in a 1×2 matrix, a 1×3 matrix, or a 1×4 matrix. In sucha case, a lenticular lens, instead of a microlens array, is used as theoptical element array 7. A lenticular lens is constituted by cylindricallenses disposed in the direction in which the wavelength band isdivided.

In addition, the imaging wavelength range of the band-pass filter array4 has been set to a range from 380 nm to 750 nm of visible light. Thepresent disclosure is not limited thereto, and the imaging wavelengthrange may include an ultraviolet range and/or an infrared range.

The pixel region of the pixels 8 a through 8 i illustrated in FIG. 4corresponds to a single pixel in the image sensor 9. The presentdisclosure is not limited thereto, and the pixel region of the pixels 8a through 8 i may, for example, correspond to 2×2 pixels in the imagesensor 9. In other words, the number of pixels corresponding to a singlemicrolens may be an integral multiple of the number of divided opticalregions.

In the present embodiment, as described above, the transmissionwavelength bands of the respective band-pass filters 4 a through 4 idiffer from one another. The present disclosure is not limited thereto,and the transmission wavelength bands (optical characteristics) of someof the band-pass filters may be identical. For example, the opticalcharacteristics of a plurality of band-pass filters may be set to beidentical in a wavelength band in which the light-receiving sensitivityof the image sensor is low. By integrating the output signals of pixelscorresponding to the stated plurality of band-pass filters, the S/Nratio can be improved.

In the present embodiment, the optical region includes at least thefirst optical region and the second optical region that have differentspectral transmittance characteristics, but the present disclosure isnot limited thereto. The optical region may include at least a firstoptical region and a second optical region that have differentpolarization characteristics. In place of the band-pass filter array 4,polarizers with different polarization directions may be disposed in therespective optical regions, and thus image information that is based onlight having different polarization components can be obtainedsimultaneously. In this case as well, if a reflective wire-gridpolarizer, for example, is used as a polarizer, a ghost image mayappears, as in the problem of the present disclosure. Through aconfiguration that is equivalent to the configuration of the presentembodiment, a plurality of images that mutually differ in terms of theirpolarization characteristics can be obtained simultaneously by using asingle imaging optical system under a plurality of polarizationconditions. A high-precision imaging apparatus for image sensing withlittle ghost image can be obtained.

In the present embodiment, the optical absorption filter serving as theoptical absorption member 6 is disposed between the lens optical systemL and the optical element array 7. The present disclosure is not limitedthereto, and the optical absorption filter may be integrated with theoptical element array 7. Alternatively, as illustrated in FIG. 6, theoptical absorption filter may be integrated with the image sensor 9.

In addition, the optical element array 7 may be integrated with theimage sensor 9. Alternatively, the microlenses 13 (FIG. 5) may beprovided between the optical element array 7 and the image sensor 9, andthe optical element array 7 may be integrated with the image sensor 9with the microlenses 13 (FIG. 5) interposed therebetween. Through thisconfiguration, positioning can be achieved in a wafer process, which canfacilitate positioning and increase the accuracy in positioning.

The present disclosure may also be applied to an imaging apparatus otherthan the imaging apparatus that includes an optical system including anoptical function element and the optical element array. For example,ghost light can be reduced even in a case in which an optical functionelement and an optical element array are not provided, as in a typicaldigital camera. For example, reflected light from an image sensor, or inother words, ghost light is reflected by a lens optical system and theinside of a lens barrel. A ghost image may appear due to such reflectedlight. In an imaging apparatus that includes at least a lens opticalsystem and an image sensor, by disposing, between the lens opticalsystem and the image sensor, an optical element that absorbs at leastvisible light and that has substantially uniform optical absorptioncharacteristics across the entire region therein through which lightpasses, a high-precision imaging apparatus with little ghost image canbe provided.

Second Embodiment

FIG. 9 is a schematic diagram illustrating an imaging apparatus 100Baccording to the present embodiment.

The imaging apparatus 100B according to the present embodiment differsfrom the imaging apparatus 100A according to the first embodiment inthat a polarizer 16 and a quarter-wave plate 17 are provided in place ofthe optical absorption filter serving as the optical absorption member6. Hereinafter, primarily the differences from the first embodiment willbe described, and detailed descriptions of similar content will beomitted.

As illustrated in FIG. 9, the imaging apparatus 100B includes thepolarizer 16 and the quarter-wave plate 17, which serve as the opticalabsorption member 6, disposed between the second lens 5 and the opticalelement array 7.

The polarizer 16 is an absorptive linear polarizer that transmits lightvibrating in a direction of a specific polarization axis. Thequarter-wave plate 17 is a phase plate that converts linearly polarizedlight to circularly polarized light or to elliptically polarized light.The polarizer 16 is disposed in the optical absorption member 6 towardthe band-pass filter array 4, and the quarter-wave plate 17 is disposedin the optical absorption member 6 toward the image sensor 9.

It is to be noted that the polarizer 16 and the quarter-wave plate 17 donot need to be disposed at the positions illustrated in FIG. 9. Forexample, the polarizer 16 and the quarter-wave plate 17 may be disposedbetween the band-pass filter array 4 and the second lens 5.Alternatively, the polarizer 16 may be disposed between the band-passfilter array 4 and the second lens 5, and the quarter-wave plate 17 maybe disposed between the second lens 5 and the optical element array 7.

The imaging apparatus 100A according to the first embodiment has anadvantage in that ghost light can be reduced with a simpleconfiguration. However, the ghost light cannot be removed completely. Inorder to increase the effect of removing the ghost light (hereinafter,referred to as a ghost light removal effect), it is desired that thetransmittance of the optical absorption filter be reduced. However, ifthe transmittance of the optical absorption filter is reduced, thequantity of light that contributes to a signal for a captured image isreduced. In this manner, there is a trade-off between the ghost lightremoval effect and the increase in the imaging sensitivity.

With the imaging apparatus 100B according to the present embodiment, byusing the polarization characteristics of light, ghost light can beremoved completely in principle.

Hereinafter, with reference to FIGS. 10A through 10D, a principle inwhich ghost light is removed by using the polarization characteristicsof light will be described.

FIG. 10D is an enlarged schematic diagram illustrating part of theimaging optical system illustrated in FIG. 9. Specifically, FIG. 10Dillustrates the configuration of the optical system extending from theband-pass filter array 4 to the vicinity of the image sensor 9. It is tobe noted that some of the optical elements are omitted.

Signal light that has passed through the band-pass filter array 4 andthe second lens 5 passes through the polarizer 16 that is disposed inthe optical axis. The polarizer 16 transmits only the light thatvibrates in the y-axis direction illustrated in FIG. 10A. When the lightpasses through the polarizer, a linear polarization component thatvibrates in the direction of the transmission axis (y-axis) of thepolarizer is extracted, and a polarization component that vibrates inthe direction orthogonal to the transmission axis (x-axis direction) isblocked. For example, when the signal light is visible light and isunpolarized or circularly polarized, the quantity of light transmittedthrough the polarizer 16 is reduced to approximately 35% to 45% of thequantity of the incident light.

When the light from the object 1 is unpolarized or circularly polarized,the transmission axis of the polarizer 16 may extend in the x-directionor the y-direction. In the meantime, when the light from the object 1 islinearly polarized, the polarizer 16 is disposed such that the directionof the transmission axis thereof is parallel to the polarizationdirection of the light from the object 1. In FIG. 10D, the polarizationdirection of signal light 18 that has passed through the polarizer 16 isthe y-axis direction. In that case, the direction in which the electricfield of the signal light 18 vibrates is the y-axis direction, asillustrated in FIG. 10A.

Subsequently, the signal light 18 passes through the quarter-wave plate17. Thus, the linearly polarized signal light changes to circularlypolarized light. The quarter-wave plate 17 is disposed in the opticalaxis such that a crystallographic axis 22 of the quarter-wave plate 17extends in a direction that is at an angle of +45 degrees or −45 degreesrelative to the y-axis. The vibration of the electric field of signallight 19 that has passed through the quarter-wave plate 17 propagates inthe z-axis direction while rotating along the xy-plane, as illustratedin FIG. 10B.

The circularly polarized signal light 19 is received by the image sensor9. As in the first embodiment, part of the light rays that have reachedthe image sensor 9 is reflected by the surface of the image sensor 9.The reflected light may become ghost light 20.

The circularly polarized ghost light 20 passes through the quarter-waveplate 17 and changes to linearly polarized light. The polarizationdirection of ghost light 21 is orthogonal to the polarization directionof the signal light 18. The electric field of the ghost light 21vibrates in the x-axis direction, as illustrated in FIG. 10C. The ghostlight 21 is then incident on the polarizer 16. However, the polarizationdirection of the ghost light 21 is orthogonal to the direction of thetransmission axis of the polarizer 16, and thus the ghost light 21 doesnot pass through the polarizer 16 and is absorbed by the polarizer 16.As a result, the ghost light 21 does not reach the band-pass filterarray 4 that could have served as a reflection surface, and thus a ghostimage does not appear.

According to the imaging apparatus 100B, of the light from the object 1,only linearly polarized light is received. Therefore, there is anadvantage in that an effect that can be obtained when a polarizationfilter is attached to a typical camera can be obtained. For example, ina case in which light is reflected by the surface of the object 1, thereflection of the light by the surface can be reduced. In addition, aghost image appearing due to reflected light from a water surface or aglass surface can be removed. A clear image of the object 1 can becaptured even when imaging through a glass.

In addition, reflected light from the water vapor in the air can beremoved, and thus a high-contrast image of, for example, the tones ofthe blue sky, the surface of a mountain, or a building can be captured.

In addition, when the light from the object 1 is unpolarized orcircularly polarized, the transmission axis of the polarizer 16 mayextend in any direction. Therefore, the polarizer 16 may be integratedwith the quarter-wave plate 17. By providing a mechanism for rotatingthe integrated element to a predetermined angle, an image that is basedon light of a desired polarization state can be captured.

In the present embodiment, an example in which the quarter-wave plate 17is used has been illustrated. However, the performance of a typical waveplate is greatly dependent on the wavelength of light to be used.Therefore, in the range of visible light, for example, it is notpossible to obtain a constant phase difference without a variation.

By using an achromatic wave plate as a wave plate, flat phasecharacteristics can be obtained in a broad wavelength band. Anachromatic wave plate can be obtained by combining two crystals havingdifferent dispersion characteristics. Any one from a broad range ofknown achromatic wave plates can be used as the achromatic wave plate.By using an achromatic wave plate, the ghost light removal effect can beobtained. In a case in which the wavelength range is narrow or a ghostimage is permitted to a certain degree, a typical wave plate may beused.

Third Embodiment

An imaging apparatus 100C according to the present embodiment differsfrom the imaging apparatus 100A according to the first embodiment inthat a light-blocking region is provided in an optical region L1.

FIG. 11A is a schematic diagram illustrating the imaging apparatus 100Caccording to a third embodiment. The imaging apparatus 100C according tothe present embodiment includes a lens optical system L having anoptical axis V, an optical element array K disposed at or in thevicinity of the focal point of the lens optical system L, an imagesensor N, and a signal processor C.

The lens optical system L includes the optical region L1 that includes aplurality of optical regions, a stop S that includes a plurality ofopenings, and a lens L2 that condenses the light that has passed throughthe stop S. The optical region L1 is disposed on a side of the stop Swhere the object is located. The lens L2 is disposed on a side of thestop S where the image sensor is disposed. The optical region L1 isdisposed in the vicinity of the stop S. The vicinity as used herein, forexample, refers to a range within a distance that is equal to or lessthan one-half the diameter of the stop and includes a case in which theoptical region L1 is in contact with the stop S. The lens optical systemL in the present embodiment is an image-side telecentric optical system.

FIG. 11B illustrates a positional relation between the plurality ofoptical regions in the optical region L1 illustrated in FIG. 11A and theplurality of openings in the stop S. FIG. 11B is a front view of theoptical region L1 and the stop S as viewed from the side of the object.FIG. 11A is a sectional view taken along the XIA-XIA line illustrated inFIG. 11B.

The optical region L1 includes nine spectral filters squarely arrayed ina 3×3 matrix. Regions in which first, second, third, and fourth spectralfilters are provided are located symmetrically to respective regions inwhich ninth, eighth, seventh, and sixth spectral filters are provided,with respect to the optical axis V of the lens optical system L. Theshape of each of the spectral filters is a square, and the spectralfilters have the same area. However, the shapes or the areas of theoptical regions may differ from one another. The nine spectral filtershave spectral characteristics of transmitting light in mutuallydifferent first through ninth wavelength bands. The first through ninthwavelength bands may be wavelength bands included in a visible lightrange or a near-infrared range.

Such spectral filters can be obtained by forming a dielectric multilayerfilm on one side or both sides of the respective spectral filters. Thestop S having the nine openings is disposed on an image side of theoptical region L1. The nine openings face the respective nine spectralfilters. To face as used herein means that a spectral filter is disposedclose to an opening so as to face the opening in the direction of theoptical axis. Hereinafter, the regions in the respective nine spectralfilters that face the openings are referred to as first through ninthoptical regions (D1 through D9). The optical regions may also bereferred to as optical transmission regions. In addition, regions in therespective nine spectral filters other than the regions that face theopenings may be referred to as first through ninth light-blockingregions. The regions in the stop S that face the light-blocking regionsmay be formed by an optical absorption member. The optical absorptionmember has substantially uniform optical absorptance across a regionthrough which light passes. In addition, the optical absorption memberhas substantially the same optical absorptance in the wavelength bandsof light that passes through the first through ninth spectral filters.That the optical absorptance is substantially uniform across a regionthrough which the light passes means that the optical absorptance perunit area is identical across the region through which the light passesor that a relative error in the optical absorptance per unit area iswithin 10% in the region through which the light passes. In addition,that the optical absorptance is substantially the same in the wavelengthbands of light that passes through the first through ninth opticalregions means that the optical absorptance is uniform across the entirewavelength band of the light that passes through the first through ninthoptical regions or that a relative error in the optical absorptance inthe wavelength band is within 10%.

The shape of each of the openings that face the optical regions D1through D4 and D6 through D9 is a hemisphere. The shape of the openingthat faces the fifth optical region D5 is a circle. The optical regionsD1 through D4 and D6 through D9 are disposed so as not to overlapanother optical region when these optical regions are rotated by 180°about the optical axis V.

A plurality of pixels in the image sensor N are divided into pixelgroups each including nine pixels P1 through P9 that are arranged in a3×3 matrix.

The signal processor C is a signal processing circuit electricallycoupled to the image sensor N. The signal processor C processes anelectric signal outputted from the image sensor N so as to generate andrecord image information.

In the present embodiment, light that has passed through the opticalregions in the optical region L1 passes through the stop S and the lensL2 in this order and is then incident on the optical element array K.The optical element array K guides the light that has passed through theoptical regions D1 through D9 to the respective pixels P1 through P9 ofeach pixel group in the image sensor N. The signal processor C generatespieces of image information corresponding to the respective firstthrough ninth wavelength bands from pixel values obtained in the pixelsP1 through P9 and outputs the generated image information.

In FIG. 11A, light beams B2, B5, and B8 are light beams that pass,respectively, through the optical regions D2, D5, and D8 in the opticalregion L1. These light beams pass through the optical region L1, thestop S, the lens L2, and the optical element array K in this order, andthen reach an imaging surface Ni of the image sensor N. It is to benoted that, since FIG. 11A is a sectional view taken along the XIA-XIAline illustrated in FIG. 11B, the light beams that pass through theother optical regions are not illustrated in FIG. 11A.

As illustrated in FIG. 11A, the optical element array K is disposed at aposition that is in the vicinity of the focal point of the lens opticalsystem L and that is spaced apart from the imaging surface Ni by apredetermined distance.

FIG. 12A is an enlarged view of the optical element array K and theimage sensor N illustrated in FIG. 11A. FIG. 12B illustrates apositional relation between the optical element array K and the pixelsin the image sensor N. The optical element array K has a structure inwhich microlenses M1, which are optical components, are arrayed along aplane orthogonal to the optical axis. The optical element array K isdisposed such that a face in which the microlenses M1 are provided facesthe imaging surface Ni. Pixels P are disposed in a matrix in the imagingsurface Ni. As described above, the pixels P can be classified into thepixel P1 through the pixel P9.

The pixel P1 through the pixel P9 are disposed in a 3×3 matrix forming aset. The optical element array K is disposed such that a given one ofthe microlenses M1 serving as the optical components covers the pixel P1through the pixel P9 disposed in a 3×3 matrix on the imaging surface Nithat correspond to the given microlens M1. Microlenses Ms are providedon the imaging surface Ni so as to cover the surfaces of the pixels.

The optical element array K is designed such that most of the lightbeams that have passed through the respective optical regions D1 throughD9 in the optical region L1 reach the respective pixels P1 through P9 inthe imaging surface Ni. Specifically, the stated configuration isachieved by setting parameters, such as the refractive index of theoptical element array K, the distance from the imaging surface Ni, andthe radius of curvature of the surface of each microlens M1, asappropriate.

Through the configuration described above, the pixels P1 through P9generate respective pieces of image information corresponding to thelight in mutually different wavelength bands. In other words, theimaging apparatus 100C can obtain a plurality of pieces of imageinformation formed by the light in mutually different wavelength bandsby a single imaging optical system through a single instance of imaging.

In the present embodiment, the openings other than the opening in thecenter of the stop S are disposed so as not to overlap another openingwhen the stop S is rotated about the optical axis V. Accordingly, anoccurrence of ghost light can be suppressed. Hereinafter, this effectwill be described.

FIGS. 13A and 13B are illustrations for describing the effect ofsuppressing ghost light. First, an occurrence of ghost light in a casein which the openings in the stop S corresponding (facing) the opticalregions D1 through D9 are all circular will be described. FIG. 13Aillustrates a principle in which ghost light is generated in a case inwhich the optical regions D1 through D9 are all circular. FIG. 13A is anillustration in which a focus is placed on two light beams from theobject that are incident on the respective optical regions D2 and D5.

The light beam B5 passes through the optical region D5 in the opticalregion L1, the stop S, the lens L2, and the optical element array K inthis order, and then reaches the imaging surface Ni of the image sensorN. Part of the light incident on the respective pixels is detected as animage signal, and another part of the light is specularly reflected toresult in reflected light B5′. The lens optical system L is animage-side telecentric optical system, and thus the reflected light B5′is reflected in the direction normal to the imaging surface. Thereflected light B5′ passes through the optical element array K, the lensL2, and the stop S in this order, and then reaches the optical region D5in the optical region L1. The spectral distribution (wavelength band) ofthe reflected light B5′ is the same as the transmission wavelength bandof the optical region D5, and thus most of the reflected light B5′passes through the optical region D5 and returns toward to object.

The light beam B2 passes through the optical region D2 in the opticalregion L1, the stop S, the lens L2, and the optical element array K inthis order, and then reaches the imaging surface Ni of the image sensorN. Part of the light incident on the respective pixels is detected as animage signal, and another part of the light is specularly reflected toresult in reflected light B2′. The lens optical system L is animage-side telecentric optical system, and thus the reflected light B2′is reflected at an angle that is the same as the angle at which thereflected light B2′ is incident. The reflected light B2′ passes throughthe optical element array K, the lens L2, and the stop S in this order,and then reaches the optical region D8 in the optical region L1. Here,if the transmission wavelength band of the optical region D8 isdifferent from the transmission wavelength band of the optical regionD2, most of the light at wavelengths outside the transmission wavelengthband of the optical region D8 is reflected by the optical region D8.Therefore, most of the light incident on the optical region D8 isspecularly reflected and reflected light B2″ is generated. The reflectedlight B2″ passes through the stop S, the lens L2, and the opticalelement array K in this order, and then reaches the imaging surface Niof the image sensor N. Since the lens optical system L is an image-sidetelecentric optical system, the light beam that has passed through theoptical region D2 travels through the aforementioned path, and the lightthat has reached the imaging surface becomes the ghost light. Although afocus has been placed only on the optical region D2 in the precedingdescription, in reality, ghost light is also generated by light thatpasses through an optical region other than the optical region D2.

When such ghost light is generated, in addition to necessary spectralinformation, unnecessary spectral information is mixed in theinformation on the pixels. This situation prevents high-precisionspectral information from being obtained.

Subsequently, an effect of suppressing ghost light in a case in whichthe optical regions D1 through D4 and D6 through D9 are disposed so asnot to be symmetric with respect to the optical axis V, as illustratedin FIG. 11B, will be described. FIG. 13B illustrates an optical pathformed in a case in which the optical regions D1 through D9 have theshapes illustrated in FIG. 11B. In the illustration, a focus is placedon two light beams incident on the respective optical regions D2 and D5.The light beam B5 travels through the same optical path as in the caseillustrated in FIG. 13A, and the reflected light B5′ returns toward theobject. Meanwhile, the light beam B2 travels through the same opticalpath as in the case illustrated in FIG. 13A, and returns toward a regionD2′ illustrated in FIG. 11B. Therefore, most of the light beam B2′ isblocked by the stop S prior to reaching the optical region L1. In asimilar manner, with regard to all of the light beams (not illustrated)other than the light beam B5, most of the reflected light from theimaging surface is blocked by the stop S. Accordingly, ghost lightdescribed with reference to FIG. 13A is hardly generated. In otherwords, the ghost light can be suppressed with the configurationillustrated in FIG. 13B.

In this manner, as the optical regions are configured as illustrated inFIG. 11B, the ghost light can be reduced. As compared with a case inwhich all of the nine openings facing the respective optical regions D1through D9 are circular, a higher-precision spectral image can beobtained.

Fourth Embodiment

An imaging apparatus 100D according to the present embodiment differsfrom the imaging apparatus 100A according to the first embodiment inthat a light-blocking region is provided in the lens optical system L,as in the third embodiment.

FIG. 14A is a schematic sectional view illustrating the imagingapparatus 100D according to the present embodiment. The imagingapparatus 100D according to the present embodiment includes the lensoptical system L having the optical axis V, the optical element array Kdisposed at or in the vicinity of the focal point of the lens opticalsystem L, the image sensor N, and the signal processor C. Hereinafter,descriptions of what are common to those in the third embodiment areomitted, and primarily the differences will be described.

FIG. 14B illustrates a positional relation between the optical regionsin the optical region L1 illustrated in FIG. 14A and the openings in thestop S. FIG. 14B is a front view of the optical region L1 and the stop Sas viewed from the side of the object. FIG. 14A is a sectional viewtaken along the XIVA-XIVA line illustrated in FIG. 14B.

The optical region L1 includes the first through fourth optical regions(D1 through D4) that transmit light in, respectively, the first throughfourth wavelength bands, the fifth optical region (D5) that transmitslight regardless of the wavelength band thereof, and the sixth throughninth optical regions (D6 through D9) that transmit light in,respectively, the sixth through ninth wavelength bands. The firstthrough ninth optical regions are arrayed at equal intervals in a 3×3matrix. The shape of each of the optical regions is a square, and theoptical regions have the same area. However, the shapes or the areas ofthe optical regions may differ from one another.

The first through fourth and sixth through ninth optical regions may,for example, be formed by forming a filter constituted by a dielectricmultilayer film on one side or both sides of the first through fourthand sixth through ninth optical regions. The fifth optical region may beformed, for example, by a transparent glass. Alternatively, nothing maybe provided in the fifth optical region D5. In other words, the fifthoptical region D5 may be an opening. As will be described later, aportion of the stop S that faces the fifth optical region D5 is alight-blocking section (i.e., light-blocking region). Therefore, theportion of the stop S that faces the fifth optical region D5 may beformed by a member that does not transmit light, such as an opticalabsorption member. The first through fourth and sixth through ninthwavelength bands may be mutually different or some of the first throughfourth and sixth through ninth wavelength bands may be the same. Thefirst through fourth and sixth through ninth wavelength bands may, forexample, be wavelength bands included in a visible light range or anear-infrared range.

The light-blocking region in the stop S has substantially uniformoptical absorptance across the region through which the light passes, asin the third embodiment, and has substantially the same opticalabsorptance in the wavelength bands of the light that passes through thefirst through ninth optical regions. That the optical absorptance issubstantially uniform across the region through which the light passesmeans that the optical absorptance per unit area is identical across theregion through which the light passes or that a relative error in theoptical absorptance per unit area is within 10% in the region throughwhich the light passes. In addition, that the optical absorptance issubstantially the same in the wavelength bands of the light that passesthrough the first through ninth optical regions means that the opticalabsorptance is identical across the entire wavelength band of the lightthat passes through the first through ninth optical regions or that arelative error in the optical absorptance in the wavelength band iswithin 10%.

The stop S has the openings at positions corresponding to the opticalregions D1 through D4 and D6 through D9. A portion of the stop S thatfaces the optical region D5 is a light-blocking section that does nottransmit light. Therefore, the light that has passed through the opticalregion D5 is not incident on pixels in the image sensor N. In theexample illustrated in FIG. 14B, the area of each opening isapproximately 70% of the area of the facing optical region, but thepresent disclosure is not limited thereto.

In the present embodiment, the light that has passed through the opticalregions in the optical region L1 passes through the stop S and the lensL2 in this order and is then incident on the optical element array K.The optical element array K guides the light that has passed through theoptical regions D1 through D4 and D6 through D9 to the respective pixelsP1 through P4 and P6 through P9 of each pixel group in the image sensorN. The signal processor C generates pieces of image informationcorresponding to the respective first through fourth and sixth throughninth wavelength bands from pixel values obtained in the pixels P1through P4 and P6 through P9 and outputs the generated imageinformation. Here, since the portion of the stop S that corresponds tothe optical region D5 is a light-blocking section, the light beam thathas passed through the optical region D5 does not reach the pixel P5.Therefore, a pixel value is not obtained from the pixel P5.

In FIG. 14A, the light beam B2 passes through the optical region D2 inthe optical element L1, and the light beam B8 passes through the opticalregion D8 in the optical element L1. The light beams B2 and B8 passthrough the optical region L1, the stop S, the lens L2, and the opticalelement array K in this order, and then reach the imaging surface Ni ofthe image sensor N. Since FIG. 14A is a sectional view taken along theXIVA-XIVA line illustrated in FIG. 14B, the light beams that passthrough the other optical regions are not illustrated.

In the present embodiment, the portion of the stop S that faces theoptical region D5 blocks light, and thus crosstalk light can besuppressed. Hereinafter, this effect will be described.

FIGS. 15A and 15B are illustrations for describing the effect ofsuppressing crosstalk light. First, an occurrence of crosstalk light ina case in which the optical region D5 transmits light in the fifthwavelength band and the portion of the stop S that faces the opticalregion D5 does not block light will be described. FIG. 15A illustratescrosstalk light between adjacent pixels in a case in which the portionof the stop S that faces the optical region D5 does not block light.Each of the arrows indicates a direction in which crosstalk lightoccurs. In the pixel P1, crosstalk light occurs with the three pixelsP2, P4, and P5. In the pixel P2, crosstalk light occurs with the fivepixels P1, P3, P4, P5, and P6. In the pixel P5, crosstalk light occurswith the eight pixels P1 through P4 and P6 through P9. In other pixels,crosstalk light occurs in a similar manner.

When such crosstalk light occurs, in addition to necessary spectralinformation, unnecessary spectral information is mixed in theinformation on the pixels. This situation prevents high-precisionspectral information from being obtained.

FIG. 15B illustrates crosstalk light between adjacent pixels occurringin a case in which the portion of the stop S that faces the opticalregion D5 blocks light, as in the present embodiment. In the pixel P1,crosstalk light occurs with the two pixels P2 and P4. In the pixel P2,crosstalk light occurs with the four pixels P1, P3, P4, and P6. In otherpixels, crosstalk light occurs in a similar manner. In the pixel P5,however, since the portion of the stop S that faces the optical regionD5 blocks light, crosstalk light with another pixel does not occur.

In this manner, in the present embodiment, since the portion of the stopS that faces the optical region D5 blocks light, crosstalk light can bereduced. Therefore, as compared with a case in which the portion of thestop S that faces the optical region D5 does not block light,higher-precision spectral information can be obtained.

When the position of the stop S that faces the optical region D5 blockslight, the number of kinds of spectral images that can be obtained isreduced from nine to eight. However, in an intended use in which thenumber of necessary pieces of spectral information is eight or less, theintroduction of a light-blocking section is effective in reducingcrosstalk light.

In the present embodiment, the optical region D5 blocks light, and thusan occurrence of ghost light can also be suppressed. Hereinafter, thiseffect will be described.

FIGS. 16A and 16B are illustrations for describing the effect ofsuppressing ghost light. First, an occurrence of ghost light in a casein which the optical region D5 transmits light in the fifth wavelengthband and the portion of the stop S that faces the optical region D5 doesnot block light will be described. FIG. 16A illustrates a principle inwhich ghost light occurs in a case in which the portion of the stop Sthat faces the optical region D5 does not block light. The followingdescription is given while a focus is placed only on the light beam B2that passes through the optical region D2. The light beam B2 passesthrough the optical region D2 in the optical region L1, the stop S, thelens L2, and the optical element array K in this order, and then reachesthe imaging surface Ni of the image sensor N. Here, part of the lightincident on the respective pixels is detected as an image signal, andanother part of the light is specularly reflected to result in thereflected light B2′. The reflected light B2′ passes through the opticalelement array K, the lens L2, and the stop S in this order and thenreaches the optical regions D5 and D8 in the optical region L1. Here, ina case in which each optical region is formed by a dielectric multilayerfilm and the wavelength band of the light that passes through theoptical region D2 is different from the wavelength bands of the lightthat passes through the optical regions D5 and D8, the reflected lightB2″ is generated. This is because most of the light at wavelengthsoutside the transmission wavelength band is reflected by a dielectricmultilayer film, and most of the light incident on the optical regionsD5 and D8 is thus specularly reflected. The reflected light B2″ passesthrough the stop S, the lens L2, and the optical element array K in thisorder, and then reaches the imaging surface Ni of the image sensor N.The light that has reached the imaging surface through theabove-described path forms a ghost image. Although a focus has beenplaced only on the optical region D2 in the preceding description, inreality, a ghost image is also generated by the light that passesthrough regions other than the optical region D2.

When such a ghost image is generated, in addition to necessary spectralinformation, unnecessary spectral information is mixed in theinformation on the pixels. This situation prevents high-precisionspectral information from being obtained.

FIG. 16B illustrates a principle in which ghost light occurs in a casein which the portion of the stop S that faces the optical region D5blocks light, as in the present embodiment. In FIG. 16B as well, a focusis placed only on the light beam B2 that passes through the opticalregion D2. Some of the light beam B2 is specularly reflected by theimaging surface Ni, and the reflected light B2′ is generated, as in thecase illustrated in FIG. 16A. The reflected light B2′ passes through theoptical element array K and the lens L2. Part of the reflected light B2′then reaches the light-blocking region of the stop S that faces theoptical region D5 and is absorbed thereby, and another part of thereflected light B2′ reaches the optical region D8. As in the caseillustrated in FIG. 16A, most of the light incident on the opticalregion D8 is specularly reflected and the reflected light B2″ isgenerated. The reflected light B2″ reaches the imaging surface Ni of theimage sensor N, as in the case illustrated in FIG. 16A. The light thathas reached the imaging surface through the above-described path forms aghost image.

When such a ghost image is generated, in addition to necessary spectralinformation, unnecessary spectral information is mixed in theinformation on the pixels. However, the amount of the unnecessaryspectral information is reduced as compared with that in the caseillustrated in FIG. 16A.

In this manner, according to the present embodiment, the stop S includesthe light-blocking section at the position that faces the optical regionD5, and thus a ghost image can be reduced. Therefore, as compared with acase in which the light-blocking section is not provided,higher-precision spectral information can be obtained.

Fifth Embodiment

FIG. 17 is a schematic diagram illustrating an overall configuration ofa spectral imaging system 30 that includes an imaging apparatus 31.

As illustrated in FIG. 17, the spectral imaging system 30 includes theimaging apparatus 31 and a signal processing device 32 that processes asignal outputted from the imaging apparatus 31. It is to be noted thatthe signal processor C described above corresponds to the signalprocessing device 32.

Any one of the imaging apparatuses 100A through 100D according to thepresent disclosure can be used as the imaging apparatus 31. Through thisconfiguration, the signal processing device 32 can process a signal thatis based on information on the light in which ghost light has beenreduced. The signal processing device 32 processes a signal outputtedfrom the imaging apparatus 31 and generates a video signal. A display 37displays a two-dimensional spectral image on the basis of the videosignal generated by the signal processing device 32. It is to be notedthat the video signal, for example, is a luminance and color differencesignal of each pixel.

The signal processing device 32 includes an image calculator 33, animage memory 34, a spectrometer 35, and an image output unit 36.

The image calculator 33, for example, carries out band-pass filterprocessing, calibrates the sensitivity of a microlens array, correctscrosstalk between pixels in an image sensor, and calculates a videosignal. The image calculator 33 generates a two-dimensional imagecorresponding to the wavelengths of the band-pass filter.

The image memory 34 records the two-dimensional image corresponding tothe wavelengths of the band-pass filter in the form of digital data. Forexample, the image memory 34 is constituted by a frame memory.

The spectrometer 35 reads out the two-dimensional image data from theimage memory 34 and processes the two-dimensional image data. Thespectrometer 35 generates two-dimensional image data of each wavelengthrange and analyzes the two-dimensional image data. The result of theanalysis is represented in a graph.

The image output unit 36 converts the data represented in a graph into avideo signal.

The signal processing device 32 may be constituted by a semiconductorelement or the like. The signal processing device 32 may typically beimplemented by an image signal processor (ISP). A computer program thatimplements the function of each component is installed in a memoryinside the ISP. A processor in the ISP may successively execute thecomputer program, and thus the function of each component may beimplemented. In this manner, the signal processing device 32 may beconstituted only by hardware or may be implemented by a combination ofhardware and software.

The display 37 displays a two-dimensional spectral image on the basis ofa video signal.

In place of the signal processing device 32, an external device, such asa personal computer, that can directly connect to the imaging apparatus31 may be used to process a signal outputted from the imaging apparatus31.

In the present disclosure, all or a part of any of unit, device,element, member part or portion, or any of functional blocks in theblock diagrams shown in FIGS. 11A, 14A, and 17 may be implemented as oneor more of electronic circuits including, but not limited to, asemiconductor device, a semiconductor integrated circuit (IC) or alarge-scale integration (LSI). The LSI or IC can be integrated into onechip, or also can be a combination of plural chips. For example,functional blocks other than a memory may be integrated into one chip.The name used here is LSI or IC, but it may also be called system LSI,very-large-scale integration (VLSI), or ultra-large-scale integration(ULSI) depending on the degree of integration. A field-programmable gatearray (FPGA) that can be programmed after manufacturing an LSI or areconfigurable logic device that allows reconfiguration of theconnection or setup of circuit cells inside the LSI can be used for thesame purpose.

Further, it is also possible that all or a part of the functions oroperations of the unit, device, part or portion are implemented byexecuting software. In such a case, the software is recorded on one ormore non-transitory recording media such as a ROM, an optical disk or ahard disk drive, and when the software is executed by a processor, thesoftware causes the processor together with peripheral devices toexecute the functions specified in the software. A system or apparatusmay include such one or more non-transitory recording media on which thesoftware is recorded and a processor together with necessary hardwaredevices such as an interface.

An imaging apparatus according to the present disclosure can beeffectively used as an imaging apparatus for a food analyzer camera, askin analyzer camera, an endoscope camera, a capsule endoscope, anin-vehicle camera, a surveillance camera, a digital still camera, adigital video camera, and so forth.

What is claimed is:
 1. An imaging apparatus, comprising: a lens opticalsystem that includes a lens and has optical regions, the optical regionsincluding first through nth optical regions, n being an integer equal toor greater than 2; an image sensor on which light that has passedthrough the first through nth optical regions is incident, the imagesensor including pixel groups and having an imaging surface thatreflects a part of the light that has passed through the first throughnth optical regions, the pixel groups each including n pixels of firstthrough nth pixels; an optical element array in which optical componentsare arrayed, the optical element array being disposed between the lensoptical system and the image sensor, the optical components each guidingthe light that has passed through the first through nth optical regionsto the respective first through nth pixels in each of the pixel groups;and an optical absorption member on which the part of the light isincident, wherein an optical absorptance of the optical absorptionmember is substantially uniform across the entire wavelength bands ofthe light that has passed through the first through nth optical regionsand is substantially uniform across the entire optical absorptionmember.
 2. The imaging apparatus according to claim 1, wherein theoptical absorption member is disposed between the optical regions andthe image sensor and absorbs at least first light in a first wavelengthband and second light in a second wavelength band, the first light beingcapable of passing through the first optical region, the second lightbeing capable of passing through the second optical region.
 3. Theimaging apparatus according to claim 2, wherein at least one selectedfrom the group of the first and second optical regions has opticalcharacteristics of transmitting visible light, and wherein the opticalabsorption member absorbs at least the visible light.
 4. The imagingapparatus according to claim 2, wherein the lens optical system furtherincludes a stop, and wherein the optical regions are disposed at thestop or in the vicinity of the stop.
 5. The imaging apparatus accordingto claim 2, wherein the first optical region differs from the secondoptical region in terms of at least one selected from the group ofspectral transmittance characteristics and polarization characteristics.6. The imaging apparatus according to claim 1, wherein the opticalabsorptance of the optical absorption member is uniform across theentire wavelength bands of the light that has passed through the firstthrough nth optical regions, or a relative error in the opticalabsorptance in the entire wavelength bands is within 10%, and whereinthe optical absorptance of the optical absorption member per unit areais uniform across the entire optical absorption member, or a relativeerror in the optical absorptance of the entire optical absorption memberper unit area is within 10%.
 7. The imaging apparatus according to claim2, further comprising: at least two narrow band-pass optical filtersdisposed in the optical regions, the at least two narrow band-passoptical filters differ in transmission wavelength bands thereof.
 8. Theimaging apparatus according to claim 2, wherein the optical elementarray is a lenticular lens.
 9. The imaging apparatus according to claim2, wherein the optical element array is a microlens array.
 10. Theimaging apparatus according to claim 2, wherein the optical elementarray is integrated with the image sensor.
 11. The imaging apparatusaccording to claim 2, further comprising: a microlens provided betweenthe optical element array and the image sensor, and wherein the opticalelement array is integrated with the microlens and the image sensor. 12.The imaging apparatus according to claim 2, wherein the opticalabsorption member is integrated with the image sensor.
 13. The imagingapparatus according to claim 2, wherein the optical absorption member isan absorptive neutral density filter, and a ratio of a quantity ofemitted light that is emitted from the absorptive neutral density filterto a quantity of incident light that is incident on the absorptiveneutral density filter is from 30% to 50% inclusive.
 14. The imagingapparatus according to claim 2, wherein the optical absorption memberincludes an absorptive linear polarizer that transmits vibrating lightthat vibrates in a direction of a polarization axis, and a phase platethat converts linearly polarized light to circularly polarized light orto elliptically polarized light, and wherein the absorptive linearpolarizer is disposed in the optical absorption member toward a side ofthe optical regions, and the phase plate is disposed in the opticalabsorption member toward a side of the image sensor.
 15. The imagingapparatus according to claim 14, wherein the phase plate is aquarter-wave plate.
 16. The imaging apparatus according to claim 14,wherein the phase plate is an achromatic wave plate.
 17. The imagingapparatus according to claim 2, wherein the first optical region hasfirst spectral transmittance characteristics of transmitting a firstnear-infrared ray in the first wavelength band, and the second opticalregion has second spectral transmittance characteristics of transmittinga second near-infrared ray in the second wavelength band, the secondwavelength band being different from the first wavelength band, andwherein the optical absorption member absorbs at least the first andsecond near-infrared rays.
 18. The imaging apparatus according to claim2, wherein n is 9, wherein, in each of the pixel groups, the firstpixel, the second pixel, the third pixel, the fourth pixel, the fifthpixel, the sixth pixel, the seventh pixel, the eighth pixel, and theninth pixel are arrayed in a 3×3 matrix, wherein the pixel groups arerepeated in a row direction and in a column direction in the imagesensor, wherein the optical element array is a microlens array thatincludes microlenses, wherein each of the microlenses in the microlensarray corresponds to one of the pixel groups, and wherein the opticalabsorption member absorbs at least the first light, the second light,third light in a third wavelength band, fourth light in a fourthwavelength band, fifth light in a fifth wavelength band, sixth light ina sixth wavelength band, seventh light in a seventh wavelength band,eighth light in an eighth wavelength band, and ninth light in a ninthwavelength band, the third light being capable of passing through thethird optical region, the fourth light being capable of passing throughthe fourth optical region, the fifth light being capable of passingthrough the fifth optical region, the sixth light being capable ofpassing through the sixth optical region, the seventh light beingcapable of passing through the seventh optical region, the eighth lightbeing capable of passing through the eighth optical region, and theninth light being capable of passing through the ninth optical region.19. An imaging apparatus, comprising: a lens optical system; an imagesensor that receives light condensed by the lens optical system; and anoptical element disposed between the lens optical system and the imagesensor, the optical element absorbing at least visible light, theoptical element having substantially uniform optical absorptioncharacteristics across the entire region of the optical element throughwhich the light passes.
 20. An imaging system, comprising: an imagingapparatus including a lens optical system that includes a lens and hasoptical regions, the optical regions including first through nth opticalregions, n being an integer equal to or greater than 2, an image sensoron which light that has passed through the first through nth opticalregions is incident, the image sensor including pixel groups and havingan imaging surface that reflects a part of the light that has passedthrough the first through nth optical regions, the pixel groups eachincluding n pixels of first through nth pixels, an optical element arrayin which optical components are arrayed, the optical element array beingdisposed between the lens optical system and the image sensor, theoptical components each guiding the light that has passed through thefirst through nth optical regions to the respective first through nthpixels in each of the pixel groups, and an optical absorption member onwhich the part of the light is incident, an optical absorptance of theoptical absorption member being substantially uniform across the entirewavelength bands of the light that has passed through the first throughnth optical regions and being substantially uniform across the entireoptical absorption member; a signal processor adapted to process a pixelsignal outputted from the imaging apparatus to generate imageinformation; and a display adapted to display an image corresponding tothe image information.